WINGS OF LEPIDOPTEEA. 



27 



When the perfect insect has quitted the cocoon it is limp and weak. Its abdomen is thick and 

 heavy, and its wings are in a rudimentary condition, but it crawls to a position where it can allow 

 them to hang down, when they can almost be seen to grow, so rapidly do they enlarge to their 

 full size and beauty, in consequence of a fluid being driven through the nervures, which subsequently 

 serve the purpose of air-tubes. The insect then flies away to seek its mate. 



In the perfect state, a Butterfly or Moth has four wings covered with scales. In some groups 

 of Moths, however, the males only have developed wings, those of the females being rudimentary, 

 and in almost all species the females are less active than the males. The interlacing nervures, or air- 

 tubes, by which the wings are traversed, form an important aid to the classification of groups. In 

 the centre of each wing we generally find an open space, called the discoidal cell. This is bounded in 

 front by the sub-costal nervure, and behind by the median nervure. Between the costa, or front of 

 the wing, and the sub-costal nervure runs another nervure, called the costal nervure ; and between the 

 median nervure and the inner margin (that part of the wing nearest to the body when the wings are 

 laid back) runs another nervure, called the sub-median nervure. These run into the costa or to 

 the lower part of the hind margin without forking; but the sub-costal and median nervures both throw 

 off several branches or nervules, as they are called to the costa or to the hind margin, which is the 

 side of the wing farthest from the body. Generally the nervures completely surround the discoidal cell, 

 but in some cases there is an open space at its extremity; and then the discoidal cell is said to be open. 

 But the neuration of the wings is much more complicated in some Moths, the discoidal cell being 

 divided longitudinally, or else small cells may be formed beyond it by the junction or crossing of 

 nervures. When most com- 



o 



plicated, the neuration re- ! 2 4 



sembles that of the Caddis- 

 flies (Trichoptera). But 

 the colours and patterns 

 of the wings are so various 

 that the study of struc- 

 tural characters is less 

 necessary than in other 

 groups of insects. 



The muscles which 

 move the wings of Lepi- 

 doptera differ little from 

 those of other insects. 

 There are two sets which 

 depress the wings : firstly, 

 a double dorsal muscle, 

 running longitudinally 

 upwards in the meso- 

 thorax; and, secondly, the 

 dorso-ventral muscles of 

 the meso- and meta-thorax, 

 which are attached to the 

 articulations of the wings 



ol>r>Aro nnrl tn flif incirlo ] > -> Papilio machaon: 3, 4, Morpho menelaus; 5, Cyclopides aracynthus: 6, Rphocia apiformis ; 7, Zygaena 

 ve, d,uu filipendulie; 8,9, 10, Sphiuxligustri; 11, Pterophorus peutadactylus. 



of the thorax beneath. 



Between these lie the nwscles, which raise the wings, and which run from the inner side of 



the back of the thorax to the legs. During flight, the thorax expands and contracts rapidly and 



constantly. 



The scales which cover the wings resemble a fine dust, which easily rubs off on the fingers ; but if 

 the wing is placed under a microscope, it is found to be covered with a great number of elegantly formed 

 scales of various shapes, some of which are represented on the adjoining woodcut. These are laid 

 over each other, like the tiles on a roof, and are attached to the wing by a small stalk, which, in 



11 



10 



SCALES OF DIFFERENT GENERA OF LEPIDOPTERA. 



